This invention is directed to the providing of a coupler for use with pipe designed to be utilized in connection with the providing of adequate drainage or passage of a liquid through such pipe. The use of coupling units or couplers per se is not new. Normally couplers fabricated from material similar to the pipe are used to hold adjacent sections of pipe together and provide an adequate seal. With respect to most prior art plastic pipe, including pipe known as double-wall pipe, the providing of a liquid impervious seal relative to the adjacent pipe sections is not of extreme importance even in drainage applications, since there is no substantial pressure in the line. However, where the nature of use for the pipe requires that sanitary sewage pass therethrough, or where pressure on the liquid carried through the pipe is present due to the pumping of the liquid or to a condition known as positive head, a condition which exists when the quantity of liquid within the pipe renders it almost full, it is desirable if not necessary that no leakage occur.
Couplers are known in the prior art associated with pipe used in the aforementioned applications. A typical type of coupler involves a polyethylene wrap secured about the adjacent ends of pipe by a fastener. These split-couplers normally require an overlap, such that a gap between the interior surface of the coupler and the exterior surface of the pipe is invariably present. Even if a gasket is placed between the adjacent pieces of pipe, installation in conjunction with the wrapped coupler may still result in a leak. This is especially the case when the pressure increases inside the pipe, as well as when the earth experiences shifts, since the force of the earth tends to break the wrapped coupler's seal as inwardly directed pressure on the pipe is changed.
It is thus apparent that the need exists for an improved coupler for pipe which provides for an effective seal similar to the invention.